Well, if you made an undirected graph the answer would be: (n*(n-1))/2
And that is (4*3)/2 that is 12/2 which is 6.
Explanation(wikipedia): Undirected graph:
An undirected graph is one in which edges have no orientation. The edge (a, b) is identical to the edge (b, a), i.e., they are not ordered pairs, but sets {u, v} (or 2-multisets) of vertices. The maximum number of edges in an undirected graph without a self-loop is n(n - 1)/2.
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